Multiple sensors of a sensing system are distributed in a vehicle to provide enhanced measurement capabilities and resolution of data by common observation of one or more emitters, transmitters, or reflectors, for example, a common target. The common target in one example comprises a vehicle, a ground installation, or a satellite. Through techniques such as interferometry, the multiple sensors determine one or more parameters of the common target, for example, location and/or shape of the common target. The accuracy to which the multiple sensors determine the parameters of the common target depends how accurately the location of each of the multiple sensors is known. The vehicle comprises a high performance navigation system to provide velocity, position, and attitude of the vehicle relative to a reference coordinate system. The navigation system is mounted in the vehicle but is usually physically separated from the sensors. The navigation system establishes navigation and orientation solutions for the vehicle relative to the reference coordinate system.
The positions of the sensors are calculated based on known static rigid distances between the navigation system and the sensors and the navigation and orientation solutions for the vehicle. As the vehicle is in motion, the vehicle bends. The bending of the vehicle causes instantaneous discrepancies between the position expressed by the master navigation system and the position experienced by the sensor. The difference between the position expressed by the master navigation system and the position experienced by the sensor is the “lever arm error.” The lever arms between the master navigation system and the sensing systems are nominally known. As one shortcoming, due to bending of the vehicle, errors are induced into the velocity, position, and orientation of the sensing system where outputs of the master navigation system are corrected based on the nominal lever arms.
One prior art solution to reduce the level arm error is to employ a smaller, lightweight, lower performance navigation system at the sensors of the sensing system. The navigation system at the sensors determines the velocity, position, and attitude of the sensors in a coordinate system relative to the sensors. As yet another shortcoming, the coordinate system defined by the navigation system at the sensor may differ from the coordinate system defined by the navigation system of the vehicle. As yet another shortcoming, spatial constraints of the vehicle may prohibit the addition of navigation systems at all the sensors. It is desirable to determine the position of all the sensors to obtain accurate measurements from all the sensors.
Thus, a need exists for accurately determining positions of all sensors in a vehicle while the vehicle is in motion.